HOUWINK’S EXPER. CONC. THE ORIGIN OF SOME DOMESTIC ANIMALS. 153 
but by mating the heterozygous hen and cock, cocks with single 
comb must appear, and this is not the case. 
The strange fact that Silky hens would be homozygous and 
Silky cocks heterozygous as far as combform is concerned, therefore 
can not be explained in the common mendelian way. 
We only might say: Silky hens form rose comb gametes, Silky cocks 
rose comb and single comb gametes. 
The results of the crosses with the Jungle-fowl agree very well 
with this supposition. 
Mating a Silky hen with a Bankiva cock we cross rose gametes 
with single gametes and so all F,’s, male or female are rose combs. 
But mating a Bankiva hen with a Silky cock we cross single 
gametes with single and rose gametes, so we get a Fy consisting 
of birds with single comb and birds with rose comb. 
All animals with rose comb in both F,’s must be heterozygous 
for combform, and the animals with single comb, coming from 
the cross Bankiva 9 X Silky ¢ breed true to comb-form while 
the former segregate. 
This is illustrated in tables 1—6. 
In the Fa of the cross Silky 9 X Bankiva ¢, the combs shew many 
variations. The difference was not only between single and not- 
single (rose) comb, but the latter was so multiform in details, 
that we thought it better to reproduce a good deal of this F9 on a 
separate plate (plate 6). 
This experience proves once more that the characters of the comb 
are not at all cleared up yet. The heredity of the comb needs 
further investigation. 
We can’t help discussing in short the results of these experi- 
ments regarding other characters as we are convinced that, even 
if our Bankiva strain should prove to be not entirely pure, they 
might be a welcome confirmation of former investigations or a 
guidance for later experiments. 
The crest. 
In F, of the first cross Bankiva 2? x Silky ¢ the crest was gold 
brown in cocks (black just behind the comb), in hens the crest was 
